1. Field of the Invention
The present invention is directed toward a test apparatus for an automotive evaporative emission system as well as a method of testing the automotive evaporative emission system.
2. Description of the Related Art
Automotive vehicles include fuel delivery systems having a fuel tank and fuel delivery lines. The fuel delivery lines typically include a plurality of conduits and associated connections operatively interconnecting the fuel tank with an internal combustion engine. A fuel pump is used to deliver the fuel under pressure from the tank to the engine via the fuel delivery lines. Many automotive vehicles are powered using gasoline as fuel. Gasoline is a volatile substance that generates gasses that, if untreated, are harmful to the environment. These gasses are generally referred to as evaporative emissions. Because they are gasses, these emissions can escape from the fuel system even through very small orifices that may present themselves throughout the fuel delivery system. Accordingly, various governmental authorities in countries throughout the world have long mandated that automotive vehicles include systems for preventing the release into the atmosphere of untreated or un-combusted fuel vapor generated in the fuel delivery system.
Thus, gasoline powered automotive vehicles typically include evaporative emission control systems that are designed to effectively deal with the evaporative emissions. Such systems typically include a vapor canister operatively connected in fluid communication with the fuel tank and the intake of the internal combustion engine. The vapor canister typically includes carbon or some other absorbent material that acts to trap the volatile evaporative emissions generated by the fuel system. A canister purge valve controls the flow of evaporative emissions between the canister and the intake of the engine. In turn, the operation of the canister purge valve is typically controlled by an onboard computer, such as the engine control module, or the like. During normal vehicle operation, and subject to predetermined operational characteristics, the canister purge valve is opened to subject the vapor canister to the negative pressure of the engine intake manifold. This purges the vapor canister of trapped gaseous emissions, effectively regenerating the canister so that it may absorb additional vapor.
During vehicle shutdown, the canister purge valve is closed and the evaporative emissions generated in the fuel system are routed from the fuel tank to the vapor canister where they are absorbed and stored for later purging as described above. During vehicle shutdown, the fuel system is effectively sealed from the ambient environment.
In addition to conventional evaporative emission control systems as described above, many governmental authorities have further mandated that these systems have self-diagnostic capabilities to determine if any leaks are present in the closed fuel system. As public concern over pollution has risen, some governmental authorities have promulgated tougher standards for automotive evaporative emission control systems. For example, the California Air Resource Board (CARB) now requires evaporative emission systems to detect leaks as small as 0.020 inches in diameter. In an effort to comply with these and other standards, there have been a number of evaporative emission systems and methods of operating same that are calculated to detect leaks as small as or smaller than 0.020 inches diameter. Many of these systems employ sensors adapted to detect the presence of a vacuum that is naturally generated in the emission space of the fuel tank after shutdown and after the fuel system has cooled. Other known evaporative emission systems employ positive pressure to test the sealed integrity of the fuel system. On-board diagnostic evaporative emission systems of the type proposed in the related art have generally worked for their intended purposes.
However, the strict standards promulgated by some governmental authorities have presented other problems during the manufacturing phase of the automotive vehicle. More specifically, certain governmental standards require original equipment manufacturers (OEM) to test the evaporative emission control systems and their associated diagnostic capabilities on at least a statistical sampling basis. In an automotive manufacturing environment, time is a precious commodity. The feasibility of any test within an automotive plant environment is strongly dependant upon the cycle time required for the test and by the flexibility of the integration of any testing procedures and equipment with the vehicle build process. This effort is further complicated by the fact that fuel systems must be tested intact. Thus, under current manufacturing processes, such tests often occur after final assembly of the fuel system and after the vehicles have been at least partially fueled. These procedures are commonly known in the art as “wet tests.” Alternatively, it is also known to test the evaporative emission control system prior to any fueling by, for example, charging the fuel system with a visible gas. This approach is known as a “smoke test” or “dry test.” Unfortunately, many of the currently available equipment and methods designed to detect leaks as small as 0.20 inches in diameter can take twenty to forty-five minutes or longer. Long test cycle times effectively preclude the opportunity to test every vehicle. Tests that are conducted on a statistical sampling basis still slow down the manufacturing process and result in increased manufacturing costs.
In view of these challenges, it is also known to delay evaporative emission control system testing until some time downstream in the vehicle delivery/sales process. For example, it has been proposed to conduct such tests at the dealership and before the vehicle is delivered to the end user. Unfortunately, the cost associated with downstream testing of the evaporative emission control system, especially in the event of a failure, further increases the cost to the manufacturer of the vehicle.
Accordingly, there remains a need in the art for a test apparatus designed to quickly and cost-effectively test the evaporative emission control system of an automotive vehicle. Furthermore, there remains a need in the art for such an apparatus that can be used to dry test the evaporative emission control system in low cycle times. In addition, there remains a need in the art for such an apparatus that can be operated under these conditions to quickly detect leaks as small as 0.20 inches diameter. There also remains a need in the art for such an apparatus that is light-weight, portable and that may be operated by a single technician in an automotive manufacturing environment. Finally, there remains a need in the art for an improved method of testing an automotive evaporative emission control system in a way that facilitates low cost, low cycle times, and convenience during the vehicle build process.